Test facilities:

After fabrication, detectors can be tested using our testing and analytical facilities:

• Standard probe station for I-V, C-V tests on test diodes
• Probe-card testing facility for STAR drift detectors (Fig. 3)
  

  Fig.3. Probe-card testing station for STAR drift detectors
• Standard probe station for I-V, C-V tests on test diodes.
• Defect analysis systems (Fig.4a and Fig.4b): I-DLTS, TSC, and TCT, with laser lights for carrier Generation (mainly used for identification and analysis of processing-related defects and irradiation-induced defects.


Fig.4a. I-DLTS/TSC system



Fig.4b. TCT system

DETECTORS MADE AND CURRENT PROJECTS

Various types of silicon detectors, including micro-strip detectors, pad detectors, drift detectors, and pixel detectors have been made over last 10 years for application in high and nuclear physics experiments and X-ray detection. Table I is a list of many of them with application and status:

Table I Detector Fabrication Status SDDPL

Detector	Application	Results/Status
400 element pad detector, ceramic overlay; three sets of charge-divided strips	NA 34 (CERN)	Used in exp. For three years Beuttenmuller et al. NIM A252 (1986) 471
512 element pad detectors, large and small interior holes	E814 (AGS, BNL)	Used for several years as multiplicity counter Giubelino, et al., NIM
192 element pad detectors square array	TRD test	Used at CERN for several years (V. Polychronakos)
192 element pad detectors square array	NA44 (CERN)	Used at CERN for several years (V. Polychronakos)
3 in diameter cylindrical silicon drift detectors	NA 45 (CERN)	First drift detector application Chen et al., IEEE TNS NS39, 619(1992), NIM A326 (1993)
STAR 6.3x6.3 cm 2 silicon drift detectors ( Fig. 5 )	SVT for STAR at RHIC	Prototype detectors for 216 detector SVT array finished Now in production at BNL and SINTEF (on-going)
50 micron pitch strip detectors	Muon Beam Finder (CERN)	In use for two years in M2 test beam (V. Polychronakos)
2 and 8 micron pitch strip detectors	Accel. Test Facility, BNL	Production used PdSi method Z. Li et al., IEEE TNS NS38 (1991)
50 micron pitch strip detectors	Current AGS	To be installed L. Remsberg, V. Polychronakos
PHOBOS test detectors	PHOBOS at RHIC	Polyimide coating test, FOXFET structures Ryan, Busza, MIT
120 element array high-rate EXAFS detectors	NSLS X19	Successful tests with 16 elements Pullia et al., NIM, BNL-62142, 62735 (on-going)
16 element strip for diffraction	NSLS	Siddons, to be installed
Radiation effects test diode gamma ray irradiation	BNL gamma source	Kraner et al., Italian Phys. Soc., Vol. 46, Baldini ed., Bologna (1994)
Radiation effects test diode Displacement damage effects	Fast neutrons	Z. Li et al., numerous publications,Still on-going
p- type pixel detectors (n+/p/p+) 48µm x 192µm pixels 120x8 array 96µm x 96µm pixels 16x60 array	Prototype for CMS at LHC	Lander, UC Davis Under test, on-going Z. Li et al., BNL-64488, to appear in NIM
n- type pixel detectors (n+/n/p+) 125µm x 125µm pixels 24x32 array 250µm x 62.5µm pixels 12x64 array ( Fig. 6 )	Prototypes for CMS at LHC	Chien, Johns Hopkins Univ. Under test, on-going Z. Li et al., BNL-64488, to appear in NIM W. Chen et al., BNL-64979
Fig.6 n- type pixel detector
n- type pixel detectors (p+/n/n+) 20µm x200µm pixels 24x32 array ( Fig. 7 )	Fermilab D0	Anderson, Kwan, Fermilab Under test, on-going Z. Li et al., BNL-64488, to appear in NIM W. Chen et al., BNL-64979
Fig.7 n- type pixel detector for D0 at Fermilab
100µm pitch large-area strip detectors 37 cm 2 sensitive area AC coupled with implanted biasing resistors ( Fig. 8 and 9 )	Prototype for PP2PP at RHIC	Guryn, Physics To be tested at Fermilab On-going
Fig.8 100 µm strip detector Fig.9 100 µm strip detector
Drift detector array for high-rate EXAFS	NSLS X19	Siddons, NSLS, to be tested On-going
X-ray active matrix pixel sensor (XAMPS) for X-ray crystallography and STEM recording data	NSLS & Biology Department	ongoing W. Chen, Z. Li, P. Rehak, J. Wall (Biology) and P. Siddons (NSLS)
P- type drift detectors for Lunar mission	NASA Lunar Mission (MSFC)	ongoing/Brian Ramsey (NASA), W. Chen, Z. Li and P. Rehak
Novel Si Strippixel detectors for PHENIX upgrade (SVX) at RHIC	PHENIX at RHIC, RBRC, RIKEN	Z. Li, H. En'Yo et al. NIM A518 (2004) 300-304
Novel Si Strippixel detectors for PHENIX upgrade (Calorimeter) at RHIC	PHENIX at RHIC, RBRC	Z. Li, E. Kistenev, et al.

RADIATION DAMAGE EFFECT HARDNESS STUDIES

Silicon radiation detectors continue to be applied to nuclear and high-energy physics experiments in both increasing complexity and quantity. Detector radiation hardness against displacement damage has become a major issue in the development of silicon tracking detectors for high-energy physics experiments in the LHC.

We have been studying the effects of fast neutron and ionizing particle radiation on the electrical properties of silicon radiation detectors, which are in widespread use as position sensitive detectors in high energy physics experiments. These damage effects will be especially important in high luminosity experiments such as at the LHC. Deep Level Transient Spectroscopy (DLTS), current shape, Thermally Stimulated Current (TSC) measurements, and Transient Current Technique (TCT) reveal specific defect structures in the silicon lattice that cause increased thermally generated current (dark current), space charge transformations (or "inversion") and short and long term annealing effects. Interactions of defects with benign, endogenous impurities in the silicon material used in these detectors offer possible amelioration of the effects of bulk displacement defects and we are pursuing methods of enhancement of these impurities (e.g., Sn, C, N, O).

The defect analysis system (DLTS, TSC, and TCT), including optical defect filling techniques, has been completed and is in routine use. The "reverse anneal" effect was correlated with a deep acceptor at E_c-0.4 eV, which is usually attributed to the di-vacancy. High carbon content material was found to exhibit not very different anneal and radiation effect properties from normal material. Positron annihilation studies have been applied to neutron-irradiated silicon for the first time and an indication of clusters (voids), which break up during anneal and supply vacancies, has been observed. Measurements on Sb doped Si detectors (material provided by NREL) and high energy Li implanted Si detectors have shown improved rad-hardness of about a factor 1.5 to 2 from standard materials. We are the first group to use low resistivity silicon materials for particle detectors with improved radiation hardness, which is a leading candidate of the actual material for detector fabrication in LHC applications. We have also first developed the technology to introduce high concentrations (10¹⁷cm^-3) of oxygen into FZSi. Oxygenated Si detectors, which are 2-4 times more radiation hard to charge particle (p,π) radiation. We have also developed cryogenic Si detectors (in collaboration with CERN RD39); MCZ Si detectors, in collaboration with Helsinki Institute of Physics and Loffe Institute, with much improved radiation hardness. Recently (June 2005), we have developed a new technology card DRIVE (detectory Recovery/Improvement Via Elavated temperature annealing), which can improve leakage current, full depletion voltage and charge collection efficiency for heavily irradiated MCZ Si detectors.

Continued measurements of material-engineered samples will be made to establish electronic effects of specific structures (di-vacancy, etc.). Further studies will continue in defect engineering, using samples such as Sn-doped FZ silicon wafers to fabricate radiation hardened detectors. We are a major contributor in a new R&D collaboration (RD48, the ROSE collaboration) devoted specifically to the development of radiation-hard silicon detectors for both ATLAS and CMS at the LHC.

For information about the Semiconductor Laboratory, please contact: Dr. Z. Li (631) 344-7604